London: A class of drugs commonly prescribed for HIV in low-income countries can cause premature ageing, a study says. The study shows these drugs damage DNA in the patient's mitochondria - the ‘batteries’ which power our cells to carry out their functions.

The findings may explain why HIV-infected people treated with such drugs sometimes show advanced signs of frailty and risk of heart disease and dementia even at an early age.

Professor Patrick Chinnery, at the Institute of Genetic Medicine, Newcastle University, says: 'HIV clinics were seeing patients who had otherwise been successfully treated but who showed signs of being much older than their years.'

'This was a real mystery. But colleagues recognised many similarities with patients affected by mitochondrial diseases - conditions that affect energy production in our cells - and referred them to our clinic,' the journal Nature Genetics quoted Chinnery as saying.

Nucleoside analogue reverse-transcriptase inhibitors (NRTIs), Zidovudine, also known as AZT, were the first class of drug developed to treat HIV, according to a Newcastle statement.

They were a major breakthrough in the treatment of the disease, greatly extending lifespan and leading the condition to be seen as a chronic (lifelong), rather than terminal, condition.

'These drugs... gave people an extra 10 or 20 years, when they would otherwise have died,' Chinnery adds.

In Europe and North America, the older NRTIs are used less commonly now due to concerns over toxicity and side-effects when taken over a long period of time.

However, as they are now off-licence and hence relatively cheap, the drugs have proved to be an important lifeline for people infected with HIV in low-income countries.